The present invention relates to a system and a method for reducing residual biocide vapor following an area decontamination process to a level safe for reentry into the area. More specifically, this invention relates to a method and apparatus for rapidly reducing the hydrogen peroxide (HP) vapor concentration from a volume in an area decontamination process. Rapid removal of the residual HP minimizes the downtime of the facility thereby increasing productivity. The present inventive apparatus comprises an aerator having a high surface area catalyst panel. Rapid HP vapor concentration reduction is achieved by optimizing air flow pattern, air transport rate, cleaned air discharge pattern, and the nature and configuration of the catalyst. The result is a 3- to 4-fold efficiency increase as compared to the prior art.
There is a need for decontaminating various enclosed areas such as hotel rooms, hospitals, airports, crew ships, clean rooms, laboratories, and many public and private facilities. These areas can be decontaminated by filling the area with a vaporized sterilizing agent. Hydrogen peroxide (HP) is commonly used in the decontamination process: a mist or vapor of hydrogen peroxide in water floods the area to be decontaminated or sterilized. During the decontamination process, HP concentrations can reach levels of 2000 ppm or more, depending on the specific process and requirements, such as degree of sterile environment needed, type of microorganism to be eradicated, and the room contents and conditions.
Following decontamination, the enclosed area must be aerated to allow for re-use of the area. To be safe, the HP concentration normally needs to be reduced to a level of less than about 1 ppm. To return the facilities to use as quickly as possible, the aeration rate (HP removal rate, expressed in g/min) should be as fast as possible, especially in hospitals and surgical rooms, in order to avoid costly downtime. Here, even accelerating the aeration time by a few minutes can matter.
Using a catalyst to accelerate the decomposition of hydrogen peroxide into water and oxygen is well known in the chemical literature. Catalysts such as activated carbon, metal oxides, and rare earth metals are known to enhance the decomposition of HP. The catalysts are typically fashioned into catalytic converters—metal substrates coated with platinum, palladium, or other metal oxides or transition metals known to decompose HP. When catalytic converters are applied to the problem of removing residual hydrogen peroxide vapor sterilant from a decontaminated area, however, the flow configuration, catalyst selection, catalyst bed formulation, and other factors complicate their successful implementation. In particular, there tends to be a decreased efficiency of the catalysts at lower concentrations of the residual HP.
In U.S. Pat. No. 7,354,551, Mielnik et al, teach a two-step process for removal of hydrogen peroxide gas from a room during a decontamination process. In the first step, HP-laden air is forced by a pump through a catalytic converter and then exits the system. HP-laden air is recycled through the system until the concentration is reduced to a level of 1 ppm or less. In the second step, a dehumidifier is used to further reduce the HP concentration and return the room atmosphere to a safe level for re-occupancy. The problem with the Mielnik method is that, because of the kinetic limitation (high flow and low residence time), the first step can take hours to achieve, and further, two separate pieces of equipment are needed, a catalytic converter and then a dehumidifier, causing undue cost and complexity in the device.
A different approach is taught in U.S. Pat. No. 7,988,911 issued to Centanni et al. Centanni teaches a two-stage method to remove residual hydrogen peroxide by passing the HP-containing gas through a catalytic converter and then through a chemical reaction system, such as thiosulphate and iodide chemicals, to remove the last traces of HP. The two-stage system is complex and costly to manufacture, and requires the use of a disposable chemical cartridge, which creates unnecessary chemical waste and further increases the cost to operate the system.
Besides the two stage processes, the prior art does not address improved efficiency of aerator through-flow and catalyst surface area optimization. Thus, a rapid residual biocide removal method with a greatly enhanced efficiency (2-3 fold) is needed, preferably by optimizing air flow pattern, air transport rate, cleaned air discharge pattern, and the nature and configuration of the catalyst.